SR API Quick Reference

This page contains a quick guide to the sr.robot3 API.

For more information, make sure you check the rest of the documentation.

Import the API

In order to use the sr.robot3 API you first need to import it into your code:

from sr.robot3 import *

Initialising your robot

Standard Initialisation

robot = Robot()

Initialisation without waiting for the start button

robot = Robot(wait_for_start=False)

# Code here runs before the start button is pressed

robot.wait_start() # wait for the start button

Initialisation with extra logging

You can also tell the robot to print extra logging information, although this will create a lot of logs.

robot = Robot(debug=True)

Selecting which board to control

If you only have one board of a given type plugged into your robot, then you can use its singular name:


If you have multiple boards of a given type plugged into your robot, you must index them by serial number:


Power Board

The outputs on the power board will turn on when you initialise your robot and turn off when your code ends.

Turn on and off the power outputs

# Turn all of the outputs on

# Turn all of the outputs off

# Turn a single output on
robot.power_board.outputs[OUT_H0].is_enabled = True

# Turn a single output off
robot.power_board.outputs[OUT_H0].is_enabled = False

Reading voltage and current

# Read the current of an individual output
current = robot.power_board.outputs[OUT_H0].current

# Read the current and voltage from the LiPo battery
voltage = robot.power_board.battery_sensor.voltage
current = robot.power_board.battery_sensor.current


The power board has an on-board piezoelectric buzzer.

# Play a standard note C6 -> C8 included for 0.5s, 0.5)

# Play a tone at 1047Hz for 1 second, 1)

# Play a tone at 500Hz tone for 2 seconds and wait for it to finish, 2, blocking=True)


Powering Motors

You can set the power of each motor on the board between -1 and 1.

If you change the power of your motor too rapidly, the overcurrent protection may be triggered.

robot.motor_board.motors[0].power = 1
robot.motor_board.motors[1].power = -1

Special motor values

This documentation refers to a feature which is only available on the physical robot kits.

Setting a motor to BRAKE is equivalent to power level 0.

# This is the same operation
robot.motor_board.motors[0].power = BRAKE
robot.motor_board.motors[0].power = 0

COAST will stop applying power to the motors. This will mean they continue moving under the momentum they had before and slowly come to a stop.

robot.motor_board.motors[0].power = COAST


You can set the position of each servo output on the board between -1 and 1.

robot.servo_board.servos[0].position = -1
robot.servo_board.servos[1].position = 1

You can also set the position to 0, which is the approximate centre.


Taking a photo

This documentation refers to a feature which is only available on the physical robot kits.

It can sometimes be useful to save a photo of what markers the robot can see:"my-photo.jpg")  # Save my-photo.jpg to the USB drive

Capturing an openCV array

This documentation refers to a feature which is only available on the physical robot kits.

Take a photo using the webcam, and return the image data as an OpenCV array:

frame =

Looking for markers

You can take a photo with the camera and search for markers:

markers =

There are various bits of information available about visible markers:

for marker in markers:  # The ID of the marker
    marker.size  # Physical size of the marker in mm.

    # Position of the marker on the image (physical kits only)
    marker.pixel_centre  # The co-ordinates of the centre of the marker
    marker.pixel_corners  # A list of corners of the marker

    # Position of the marker
    marker.position.distance  # Distance away from the camera in mm
    marker.position.horizontal_angle  # angle to the marker in radians
    marker.position.vertical_angle  # angle to the marker in radians

    # Orientation of the marker


Setting the mode of a pin

robot.arduino.pins[4].mode = OUTPUT
robot.arduino.pins[4].mode = INPUT
robot.arduino.pins[4].mode = INPUT_PULLUP

Digital Write

You can set the output for a pin of the Arduino:

robot.arduino.pins[2].mode = OUTPUT


Digital Read

You can read a digital value from the pins of the Arduino:

robot.arduino.pins[3].mode = INPUT
robot.arduino.pins[5].mode = INPUT_PULLUP

value = robot.arduino.pins[3].digital_read()
value = robot.arduino.pins[5].digital_read()

Analogue Read

You can read an analogue value from the analogue pins of the Arduino:

robot.arduino.pins[A0].mode = INPUT

value = robot.arduino.pins[A0].analog_read()


The API also makes some information about where your code is running

Starting zone for a match

zone =  # -> 0, 1, 2, or 3

Robot mode

This is set to COMP when your robot is in a match.

robot_mode = robot.mode # -> DEV or COMP

USB stick path

This is the path to where your USB stick is mounted.

You can use this to save files and information to the drive.

usb_key_path = robot.usbkey

Is simulated

A boolean value indicating whether or not the code is running in the simulator. This value is True when in the simulator and False when on the robot.

value = robot.is_simulated